Telegraph system



P 1949= e. c. HARTLEY ETAL 2,468,065

TELEGRAPH srsma Original Filed Marchlfl. 1943 2 Sheets-Sheet 1 FULARIZED Snventor: (1501965 0. HARTLEY w/LL/AM J. REY/vows April 26, 1949.

G. C. HARTLEY ET AL TELEGRAPH SYSTEM 2 Sheets-Sheet 2 Original Filed March 10, 1943 STIOP START so I00 A f fi wx z Patented Apr. 26, 18

TELEGRAPH SYSTEM George Clifford Hartley and William John Reynolds, London, England, assignors, by mesne asu lignmenta, to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Original application March 10, 1943, Serial No. 478,735, now Patent No. 2,433,362, December 30, 1947. Divided and this application April 6.

1946, Serial No. 660,100.

March 13, 1942 In Great Britain Claims. (01. 117-353) The present invention relates to telegraph systems operating with a code such as the five-unit code, and is more particularly concerned with circuit arrangements for receiving such a code, which do not involve rotating mechanical systems. The presentapplication is a division from our application Serial No. 478,735, filed March 10, 1943, now U. S. Patent 2,433,362 of Dec. 30, 1947.

Probably the most important application of the five-unit code at the present time is in the transmission of teleprinter signals where the well known start-stop principle is employed. The power required to operate a teleprinter is derived from an electric motor coupled to a rotating mechanical system, and on account of the functions which it has to perform it is necessarily an intricate and expensive machine requiring a relatively large amount of maintenance. There are certain cases where a telegraph channel is required to convey information of a limited character in which the cost of teleprinters would not be justifled, particularly where the information is not required to be recorded on paper in the usual way.

A typical case of this kind is that in which an electric power supply system includes a means for periodically reporting the indications of watt meters or other like instruments located at a distance; the necessary information can in this case be conveyed by means of a few characters, and might be used to operate appropriate indicators, instead of being typed out. Another example is the case where a circuit is used for the transmission of certain standardized orders to a distant point where they might be displayed on an indicator.

It is evident that a system suitable for this sort of service should be economical to construct and should require the minimum of maintenance. The present invention provides circuit arrangements chiefly employing ordinary commercial telephone type relays not requiring any special adjustments, and not involving any motor-driven mechanical systems. These circuits comprise a code receiver which can be used to store the characters and to use them to operate any suitable form of indicator or other receiving device.

According to the invention there is provided a telegraph receiver for start-stop code signals comprising a pendulum relay, means for releasing the relay armature from a locked position to execute free oscillations, and means for returning the armature to a locked position after a predetermined number of swings.

of embodiments and to the accompanying drawlngs, in which.

' Fig. 1 shows a schematic circuit diagram of a code receiver according to the invention; and

Fig. 2 shows a diagramused to explalmthe operation of Fig. 1.

, In order that the invention may be clearly understood, it will be assumed that the signals to be received are start-stop five-unit code signals suitable for the conventional teleprinters operating at a speed of 50 words. It will be evident, however, that the same circuits are adaptable for other codes and speeds: it is quite possible, for example, that in some of the cases mentioned above to which the invention is specially suited, the information could be conveyed on a code with fewer units; in other circumstances more than five units might be preferable.

In all machine systems using codes, it is esse tial to have some means of sending out or receiving signals at accurately spaced intervals. In teleprinters this is generally done by means of a shaft rotating at an accurately controlled speed and carrying a cam which operates contacts once per revolution. In the present invention. use is made of a pendulum relay having an armature which can execute isochronous vibrations with small damping, and which is adapted to operate contacts approximately at the centre of its travel, in such manner that the intervals between successive operations are closely equal. Such an armature might consist of a weight mounted on a flat; spring which also carries the means for operating the contacts, andmay be held in a locked position on one side when the relay winding is energised. The weight should preferably be adjustable on the spring so that the vibration frequency can be varied. The armature can be caused to execute free vibrations by cutting off the energising current, and so releasing it, and by a suitable circuit it may be given suitably timed impulses to maintain it indeflv tact" principle.

In order to simplify the circuits, any connection to the battery or other constant potential source is indicated by an arrow-head pointing 3 away from a relay, and earth connections are indicated by the conventional symbol. The positive terminal of the battery is supposed to be connected to earth, though the circuitwould operatethe other way Just as well. Generally, spark quenching arrangements, current adjusting resistances and other like accessories not essential to the invention have been omitted, and may be supplied in any suitable manner known to those skilled in the art.

The circuits are shown with all relays in the unoperated condition, that is, the condition which holds before the battery has been switched on. Actually certain relays are normally operated during the idle periods between the transmissions of the individual characters, and these will be pointed out in the course of the explanation of the operation of the circuits.

In the description of the circuits, use will be made of the terms mark" and space, and marking" and spacing." The marking condition of a line or circuit used for start-stop signals is the condition during which the circuit is temporarily idle, though ready to transmit characters, and the spacing condition is the opposite condition. The actual state of the line or circuit, that is, whether it is connected to positive or negative battery, or whether in the case of single current operation it is open or closed (and so on) during the marking condition will depend on the arrangements which have been chosen, and is' immaterial, so long as the chosen conditions are consistently maintained. The signal element which is produced by the change to the marking condition will be called a marking element or mark, and the other element is the spacing element or space. Thus the start element is always a space, and the stop element is always a "mark."

When the pendulum relay armature vibrates, it makes alternate swings from side to side and is always locked, and released from, the same side. The word swing will be used to denote one movement of the armature; a complete vibration period therefore comprises two swings.

Although in the detailed description below various particular relay timings and the like have been specified for clearness, these are not in any sense necessary to the invention, and other timings can be arranged for other cases.

General description of the code receiver circuit (Fig. 1)

The incoming signals are applied at terminal 6 to the receiving relay RR, which is preferably a polar relay having marking and spacing contacts RRM and RRS. The unit signals repeated by the relay RR are inspected by a. series of code storing relays VV, WW, XX, YY and Z2 each of which applies an earth to 2. corresponding terminal I to 5 (which may be connected as desired to a receiving apparatus or storage system of any type), when the corresponding unit signal is a space. A pendulum relay PB determines that the inspection shall be made during a short interval, say, about 5 milliseconds, in the middle of each millisecond unit interval, and a train of counting relays BB, CC, DD, EE and FF counts the swings of the pendulum relay and auses it to be locked up when the character has been received. A second pendulum relay PA is used to delay the release of the first pendulum relay PB, so that the inspection periods occur in the middle of the 20 milliseconds signal intervals. The description below is based on a 5-millisecond cacao Idle, or ready to operate condition In the working condition of the circuit it is necessary for the two pendulum relays PA and PB to be locked up and for relay HH to be operated. For this purpose a slow-release relay HHR is provided. As soon as the batteries are switched on, HH and PA operate through contacts HHR-l and PB operates through its winding d and HER-2. These contacts, however immediately break when HHR is operated by the closing of contacts HH-l, the relay HH locking itself and holding PA through its winding h and contacts HH--2 from. the earth obtained from contact RRM. The relay HHR remains operated for the whole of the time the circuit is working, Its sole purpose is to reset the idle condition of the circuit when the batteries are first switched on. After the operation of HHR, PB is held through its winding h, and contacts PA-I, AR-i, and FF--l; contacts PA-2 being now open.

Effect of the start signal On receipt of the start signal, the receiving relay RR changes its armature over to the spacing side RR-S. This operates relay AA which looks itself through its contacts AA5 and the contacts FF--2. Relay AA prepares for subsequent operation relays AR (through AA|: PA-2 being open); BB (through AA2); and VV (through AA3); and further, it prepares a locking earth for the code storing relays W to ZZ, by closing its contacts AA-4.

The removal of the earth connection from RR--M also releases the pendulum relay PA, which starts to swing. Nothing further happens until it opens the contacts PA-l which releases the other pendulum relay PB, which thereupon also starts to swing. The closing of the contacts PA-2 which occurs at about the same time, operates relay AR which applies earth to the winding d of PA through contacts Ar-2 for the purpose of locking it up on the return swing. PA plays no further part in the reception of the character. PB continues to execute a few free vibrations until it becomes locked up on the completion of the operation,

The removal of earth from RRr-M also releases relay H which opens its contacts HH-2; this is in order to prevent subsequent marking signals from aflecting relays HH'and PA. HH also closes the contacts HH-3 to prepare a locking circuit for relay FF, and an operating circuit for KK.

It will thus be seen that the start signal releases the timing relays and prepares a number of circuits for later operation.

Operation of the timing relays The working of the relays PA and PB and of the other relays will be understood from the diagram of Fig. 2. The various operations are there indicated with reference to a horizontal time scale divided at intervals of 20 milliseconds. The start element is supposed to be received at zero time; the code elements arrive at 20, 40, 60, 80 and 100,

place between 27 /2 and 32% milliseconds, and is Y made to commence when relay PB closesits contacts PBS, as will be presently explained, The relay PB must execute free vibrations at as nearly as possible 25 complete cycles per second in order" to time the inspection correctly. It is found that relays oi the type described in the above mentioned specification and adjusted to 25 cycles take about 12 milliseconds to operate their contacts after being released from the locked position. The inspection relays are high speed relays having an operate time of the order of 1 millisecond. To achieve the timing mentioned above the relay PA must introduce a delay of 14 /2 milliseconds and this will be attained if the relay is adjusted to a frequency of about 20 cycles per second. It will be understood that in practice the PA relay can be adjusted to give the exact time required for the case quoted above or to function with an inspection period of any other duration which may be convenient. 1

' Thus in Fig. 2, relay PA is released by the start signal at zero time. It opens the contacts PAI and releases PB at 14 milliseconds. PB swings over to the PBS side at about 27 /2 milliseconds. Meanwhile, Ofcourse, relay RR has changed back to the marking side for the first code element (assuming the character B to be received), but this has no immediate efiect. The changing over of the armature of relay PB has removed the earth from the inspecting relay HB and applied it to the other inspecting relay HA. These two relays should be very quick to operate, but should be given a releasing time of say, or 6 milliseconds by meansof the rectifier and condenser arrangement shown, for example. Thus HB does not release until about 32 milliseconds, while HA is operated at 27 milliseconds, so that both relays are operated together for the required period of about 5 milliseconds in the middle of the code interval. Thus the circuit leading'from the spacing contact RRS to the contacts of the counting relays is closed for this period only, through the relay contacts HAI and HBI. This can be seen from Fig. 2, where the horizontal lines marked HA and HB denote the periods during which these relays have their contacts closed: the

5 millisecond overlap is clearly shown with refer-1 ence to the operations of PB. It will be clear that the same process occurs inthe middle of each or the code intervals. At approximately 40 milliseconds, the relay PA swings back and locks up, as shown by the graph labelled PA. PB goes on swinging until locked up at about 127 milliseconds,;after the operation of relay FF as will be explained later on.

Operation of the counting and code storing relays Therelay W has been prepared for operation by the closing of contacts AA-3, and if the first code unit element is a space, it will be operated and looked through its contacts VV-l during the BB remains operated for about 50 milliseconds until about milliseconds, by reason of the resistance q shunting its winding. Relay BB also prepares W by closing its contacts BB-l which will operate in the second code interval for. the character "B". The same series of operations then follows. Relays CC, DD and EE operate one after the other, allowing 10!, YY and ZZ to operate it the corresponding code element is a space.

. When relay E has operated, by closing its contacts Ell-2 it preparesrelays FF and KK to be energised by the pendulum relay on its swing at 107 milliseconds. These relays operate at about contacts HH-l and release about 12 milliseconds later (since they are unshunted).

The relay K by closing its contacts K--l to K-5 connects earth to the terminals I .to 5 according to the setting of the code storing relays W to ZZ. This earth is obtained through contacts AA-4, and relay KK provides an alternative earth through contacts KK6 because relay AA is released before the operation is complete. When relay K is finally released at about 144 milliseconds (t2 Fig. 2) it disconnects all the code storing relays which have been operated and these relays all release at about 158 milliseconds. All the operations which have been described are diagrammatically shown in Fig. 2)'.

While the operate and release times of these relays are not of critical importance, it is necessary that thesetimes should not be so long that the code relays fail to release before about 160 milliseconds. to be transmitted so closely following the first that the interval between the stop and the start elements is reduced to 20 milliseconds. The first inspection interval for the secondcharacter can thus occur from 167% to 172 milliseconds shown at t3 in 'Fig. 2, and it is therefore clearly necessary that the code storing relays should be released before this interval.

.The swing of the pendulum relay PB at 107% milliseconds is the last effective swing, and it must be lockedup on its return at 127 milliseconds. The operation of relay FF provides the necessary locking circuit by closing its contacts FFI. In the meanwhile, the release of AA has released AR by opening its contacts AA-i. This takes the locking ground oif relay PA (now held through winding 12.) and prepares the holding circuit for PB through ARI and PA-i. When relayFF is finally released after the operation of KK, .the earth is transferred from the winding (1 This is to ensure the release of EE.

to the winding h of relay PB, and the circuit is restored to the idle condition.

It will be noted that the contacts AA-B assoelated with the winding of relay EE disconnect the shunting resistanceq when AA is released.

The timing of the release of the inspecting relays HA and BB is carried out by shunting the windings with condensers CA and CB respectively having current limiting resistances of low value connected in series, and by providing the series rectifiers JAI and JA2. The relay is energised through the rectifier and should operate very quickly as already explained, and the conseconds on the nextswing oi the relay PB. Relay It is possible for the second character denser is at the same time charged. when the circuit is broken by the pendulum relay PB, the condenser discharges through the relay holding it operated for the desired time, the other path being blocked by the rectifier. Two other rectifiers'JA2 and J3: are provided to block the undesired alternative paths through the contacts of the counting relays by which the inspecting relays could be operated.

The earth for operating the code storing relays VV to ZZ is only applied for the 5 millisecond inspection period, and in order to ensure their proper operation, their windings are shunted by condensers CV to CZ in series withcurrent limiting resistances. The condenser is charged up at the same time as the relay is energised, and when the circuit is broken at HA--l or HB-l, the condenser discharges through the winding of the relay and ensures its complete operation, and it then locks itself as already explained.

It will be understood that the final effect of receiving a character is that relay KK momentarily connects to earth any of the terminals l to 5 for which the corresponding code signal element is a space. It is assumed that these terminals will be connected to some storage or indicating device of any desired type.

Other simpler arrangements of the combined circuit are possible and will be easily prepared by those skilled in the art in accordance with the principles which have been explained.

Although the invention has been described for clearness in terms of particular embodiments, it is not intended to be limited thereto, nor to the numerical values which have been quoted as examples.

What is claimed is: v

1. A telegraph code receiver for telegraph code signals, comprising a first oscillating relay having an armature capable of oscillating freely at a predetermined rate, means for holding said armature displaced from its normal position, means for releasing said holding means to permit free oscillation of said armature, means for operating said holding means after a predetermined number of oscillations of said armature to secure said armature again in said displaced position, means for receiving a succession of code unit elements at unit intervals corresponding to the oscillations of said relay, said receiving means including a polar relay, means for inspecting said code unit elements during a predetermined short period in each unit interval, said inspecting means including the first-mentioned relay which is adapted to be released on receipt of the start signal, a second oscillating relay adapted to be released by the first oscillating relay during its first'swing, and two similar fast operating inspecting relays adapted to be operated alternately during successive swings of said second oscillating relay.

2. A telegraph code receiver for telegraph code signals, comprising a first oscillating relay having an armature capable of oscillating freely at a predetermined rate, means for holding said armature displaced from its normal position, means for releasing said holding means to permit free oscillationof said armature, means for operating said holding means after a predeterr'ined number of oscillations of said armature to secure said armature again in said displaced position, means for receiving a succession of code unit elements at unit intervals corresponding to the oscillations of said relay, said receiving means including a polar relay, means for inspecting said code unit elements during a predetermined short period in each unit interval, said inspecting means including the first-mentioned relay which is adapted to be released on receipt of the start signal, a second oscillating relay adapted to be released by the first oscillating relay during its first swing, and two similar fast operating inspecting relays adapted to be operated alternately during successive swings of said second oscillating relay, the frequency of oscillation of said second oscillating relay being such that the time interval between successive operations of its contacts is equal to the unit time interval of the code.

3. A telegraph code receiver for telegraph code signals, comprising a first oscillating relay having an armature capable of oscillating freely at a predetermined rate, means for holding said armature displaced from its normal position, means for releasing said holding means to permit free oscillation of said armature, means for operating said holding means after a predetermined number of oscillations of said armature to secure said armature again in said displaced position, means forreceiving a succession of code unit elements at unit intervals corresponding to the oscillations of said relay, said receiving means including a polar relay, means for inspecting said code unit elements during a predetermined short period in each unit interval, said inspecting means including the first-mentioned relay which is adapted to be released on receipt of the start signal, a second oscillating relay adapted to be released by the first oscillating relay during its first swing, and two similar fast operating inspecting relays adapted to be operated altematelY during successive swings of said second oscillating relay, the vibration of said second oscillating relay being such that the time interval between successive operations of its contacts is equal to the unit time interval of the code, and the vibration frequency of said first oscillating relay is adjusted so that the time interval between the receipt of said start signal and the operation of 'said first inspecting relay during the first swing of said second oscillating relay after its release is greater than one but less than two code unit intervals.

4. A telegraph code receiver for telegraph code signals, comprising a first oscillating relay having an armature capable of oscillating freely at a predetermined rate, means for holding said armature displaced from its normal position, means for releasing said holding means to permit free oscillation of said armature, means for operating said holding means after a predetermined number of oscillations of said armature to secure said armature again in said displaced position, means for receiving a succession of code unit elements at unit intervals corresponding to the oscillations of said relay, said receiving means including a polar relay, means for inspecting said code unit elements during a predetermined short period in each unit interval, said inspecting means including the first-mentioned relay which is adapted to be released on receipt of the start signal, a second oscillating relay adapted to be released by the first oscillating relay during its first swing, and two similar fast operating inspecting relays adapted to be operated alternately during successive swings of said second oscillating relay, 9. separate condenser shunted across the winding of each inspecting relay, and a separate rectifier connected in series with each inspecting relay, the capacity of the condenser being so chosen that the release of the relay is delayed by a period 5. A telegraph code receiver for telegraph code signals, comprislnga first oscillating relay having an armature capable of oscillating freely at a. predetermined rate, means for holding said armature displaced from its normal position, means for releasing said holding means to permit free oscillation of said armature, means for operating said holding means after a predetermined number of oscillations of said armature to secure said armature againin said displaced position, means for receiving a succession of code unit elements at unit intervals corresponding to the oscillations of said relay, said receiving means including a polar relay, means for inspecting said code unit elements during a predetermined short period in each unit interval, said inspecting means including the first-mentioned relay which is adapted to be released on receipt of thestart signal, a second oscillating relay adapted to be released by the first oscillating relay during its first swing, and two similar fast operating inspecting relays adapted to be operated alternately during successive swings of said second oscillating relay, a separate condenser shunted across the winding of each inspection relay, and a separate rectifier connected in series with the winding of each inspection relay, the capacity of each condenser being so chosen that the release of the associated relay is delayed by a period substantially equal to the predetermined inspection period, each inspecting relay being provided with a pair of make I contacts connected in series with the operating circuit for the code storing relays, whereby the said operating circuit is closed only for the predetermined inspection period in each code unit interval. l

6. A telegraph code receiver for telegraph code signals, comprising a first oscillating relay having an armature capable of oscillating freely at a predetermined rate, means for holding said armature displaced from its normal position, means for releasing said holding means to permit free oscillation of said armature, means for operating said holding means after apredeterminednumber of oscillations of said armature to secure said armature again in said displaced position, means for receiving a succession of code unit elements at unit intervals corresponding to the oscillations of said relay, said receiving means including a polar relay, means for inspecting said code unit elements during a predetermined short period in each unit interval, said inspecting means including the first-mentioned relay which is adapted to be released on receipt of the start signal, a

second oscillating relay adapted to be released byv the first oscillating relay during its first swing, and two similar fast operating inspecting relays adapted to be operated alternately during successive swings of said second oscillating relay, a separate condenser shunted across the winding of each inspection relay, and a separate rectifier connected in series with the winding of each inspection relay, the capacity of each condenser being so chosen that the release of the associated relay is delayed by a period substantially equal to the predetermined inspection period, each inspecting relay being provided with a pair of make contacts connected in series with the operating circuit for the code storing relays, whereby the said operating circuit is closed only for the predetermined inspection period in each" code unit interval, and a plurality of counting relays associated with said code storing relays, each code storing relay bein adapted to be connected in turn to the operating circuit by a contact operated by the corresponding counting relay.

'7. A telegraph code receiver for telegraph code signals, comprising a first oscillating relay having an armature capable of oscillating freely at a predetermined rate, means for holding said armature displaced from its normal position, means for releasing said holding means to permit free oscillation of saidarmature, means for operating said holdin means after a predetermined number of oscillations of said armature to secure said armature again in said displaced position, means for receiving a succession of code unit elements at unit intervals corresponding to the oscillations of said relay, said receiving means including a polar relay, means for inspecting said code unit elements during a predetermined short period in each unit interval, said inspecting means including the first-mentioned relay which is adapted to be released on receipt of the start signal, a second oscillating relay adapted to be released by the first oscillating relay during its first swing, and two similar'fast operating inspecting relays adapted to be operated alternately during suc-' cessive swings of said second oscillating relay, a separate condenser shunted across the winding of each inspection relay, and a separate rectifier connected in series with the winding of'each inspection relay, the capacity of each condenser being so chosen that the release of the associated relay is delayed by a period substantially equal to the predetermined inspection period, each inspecting relay being provided with a pair of make contacts connected in series with the operatin circuit for the code storing relays, whereby the said operating circuit is closed only for the predetermined inspection period in each code unit interval, each of said code storing relays having its winding shunted by a condenser adapted to be charged during the inspection period and to discharge through the relay winding when the operating circuit is opened, thereby insuring the operation of the relay.

8. A telegraph code receiver for telegraph code signals, comprising. a first oscillating relay having an armature capable of oscillating freely at a predetermined rate, means for holding said armature displaced from its normal position, means for releasing said holding means to permit free oscillation of said armature, means for operating said holding means after a predetermined number of oscillations of said armature to secure said armature again in said displaced position, means for receiving a. succession of code unit elements at unit intervals corresponding to the oscillations of said relay, said receiving means including a polar relay, means for inspecting said code unit elements during a predetermined short period in each unit interval, said inspecting means including the first mentioned relay which is adapted to be released on receipt of the start signal, a second oscillating relay adapted to be released by the first oscillating-relay during its first swing, and two similar fast operating inspecting relays adapted to be operated alternately during successive swings of said second oscillating relay, and means for locking the armature of said first oscillating relay immediately after its second swing. I

9. A telegraph code receiver for telegraph code signals, comprising a first oscillating relay having an armature capable of oscillating freely at a predetermined rate, means for holding said armature displaced from its normal position,

means for releasing said holding means to. permit free oscillation of said armature, means for operating said holding means after a predetermined number of oscillations of said armature to secure said armature again in said displaced position, means for receiving a succession of code unit elements at unit intervals, corresponding to the oscillations of said relay, said receiving means including a polar relay, means for inspecting said code unit elements during a predetermined short period in each unit interval, said inspecting means including the first-mentioned relay which is adapted to be released on receipt of the start signal, a second oscillating relay adapted to be released by the first oscillating relay during its first swing, and two similar fast operating in- 10. A telegraph code receiver for telegraph code signals, comprising a first oscillating relay having an armature capable of oscillating freely at a predetermined rate, means for holding said armature displaced from its normal position, means for releasing said holding means to permit free oscillation of said armature, means for operating said holding means after a predetermined number of oscillations of said armature to 12 secure said armature again in said displaced position, means for receiving a succession of code unit elements at unit intervals, corresponding to the oscillations of said relay, said receiving means including a polar relay, means for inspecting said code' unit elements during a predetermined short period in-each unit interval, said inspecting means including the first-mentioned relay which is adapted to be released on receipt of the start signal, a second oscillating relay adapted to be released by the first oscillating relay during its first swing, and two similar fast operating inspecting relays adapted to be operated alternately during successive swings of said second oscillating relay, said receiver being adapted to receive a five unit code and comprising five of the code storing relays and five of the counting relays, the second oscillating relay being arranged to make six single swings during the transmission of a character,

GEORGE CLIFFORD HARTLEY.

WILLIAM JOHN REYNOLDS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,967,396 Chauveau July 24, 1934 2,210,577 Fitch .Aug. 6, 1940 2,400,574 Rea et a1. May 21, 1948 

